Photographer's Note

Endurance exercise or endurance training consists of performing low- to medium-intensity exercise for long periods of time. E.g., jogging or running several miles or km to hundreds of miles; cycling dozens of miles to thousands of miles; swimming hundreds of yards or meters to dozens of miles or km.

Physical endurance is differentiated from other forms of physical stress in that in endurance exercise fatigue of the muscles and cardiovascular system do not force the effort to end. The need for sleep, the buildup of non-recyclable waste chemicals, the depletion of convertible energy stores and other needed chemicals (e.g., water, sodium), physical injury, psychological failure, or attainment of the goal will bring the effort to an end.